Castle Biosciences Presents Three New Clinical Studies at ASCO 2017 Highlighting the Accuracy and Performance of the DecisionDx-Melanoma Gene Expression Profile Test for Cutaneous Melanoma

Chicago, IL – June 5, 2017 – Castle Biosciences, Inc., a provider of molecular diagnostics to improve cancer treatment decisions, today announced that three abstracts detailing results from studies of DecisionDx®-Melanoma were presented at the 2017 American Society of Clinical Oncology (ASCO) Annual Meeting being held in Chicago, IL from June 2-6. Presentations included an interim analysis of a prospective, multicenter registry study, test performance in Stage III cutaneous (skin) melanoma patients and an analysis of test performance in patients with melanoma of the head and neck. The molecular diagnostic test uses tumor biology to provide an individual risk of recurrence in cutaneous melanoma patients.

Prospective, Multicenter Registry Study
In the abstract, “Interim Analysis of Survival Outcomes in a Prospective Multicenter Cohort Evaluating a Prognostic 31-Gene Expression Profile (GEP) Test for Melanoma” (Abstract #9573), outcome results from 322 patients with Stage I-III cutaneous melanoma who received DecisionDx-Melanoma testing were discussed. The DecisionDx-Melanoma test was performed to determine molecular class for each patient, with a Class 1 result indicating low 5-year risk of metastasis and a Class 2 result indicating high risk. Endpoints of recurrence-free survival (RFS), distant metastasis-free survival (DMFS) and overall survival (OS) were assessed using Kaplan-Meier and Cox regression analyses.

The abstract reports an interim analysis at year 3 of an anticipated 5-year prospective, multicenter registry study. Median follow-up time for this analysis was 1.5 years for event-free patients.

Summary of Study Results:

Interim analysis results confirm the association between DecisionDx-Melanoma class result and outcomes (p<0.0001).

Consistent with prior studies, significantly different recurrence rates were observed for low-risk Class 1 (2%) and high-risk Class 2 (27%) groups, with 1.5-year RFS rates of 97% for patients in the Class 1 group compared with 77% for those in the Class 2 group (p<0.0001).

80% (20 of 25) of patients who experienced recurrences during the study had a Class 2 GEP result. In comparison, 40% (10 of 25) of patients with recurrences had a sentinel lymph node- (SLN) positive result and 60% (15 of 25) had ulcerated primary tumors.

In this study, 83% (10 of 12) of patients who developed distant metastases were identified as high-risk by the DecisionDx-Melanoma test, compared to 50% (6 of 12) who had a SLN-positive result, indicating that the GEP test can improve the identification of high-risk cutaneous melanoma patients.

High negative predictive values (NPV) of 98% for recurrence and 99% for distant metastasis demonstrate that a Class 1 outcome was associated with a low risk of metastasis during the study.

“It is important to identify early stage patients with melanoma who are at an increased risk of recurrence so that appropriate surveillance can be provided,” commented study co-investigator Kelly M. McMasters, M.D., Ph.D., Chair of the Department of Surgery, University of Louisville. “The results from this interim analysis confirming the association of the DecisionDx-Melanoma class with patient outcome align with my experience in clinical practice showing that assessing tumor biology can provide important, clinically impactful prognostic information.”

Using Cox multivariate analysis, the DecisionDx Melanoma test was shown to be a significant predictor of distant metastasis (p=0.04), as seen in the table below:

The DecisionDx-Melanoma test showed significant separation of risk for distant metastasis (p=0.04) and melanoma-specific death (p=0.01) in Stage IIIA patients. The test identified as high risk 66% (19 of 29) of Stage IIIA patients who experienced distant metastasis and 80% (12 of 15) of Stage IIIA patients who died from melanoma, correlating with a NPV of 91%. (See table below.)

These results suggest that GEP testing may be useful in identifying Stage IIIA patients who would benefit from currently available adjuvant therapies and/or enrollment in clinical trials.

Results from a subset of patients (n=125) who underwent completion lymph node dissection (CLND) suggest that DecisionDx-Melanoma testing could potentially complement the CLND procedure for risk assessment in SLN-positive patients as sensitivity for distant metastatic disease improved to 87% when GEP testing was incorporated, compared to 45% with non-SLN status alone.

“The results from this study demonstrate that the DecisionDx-Melanoma test is an accurate predictor of distant metastasis and survival for patients with Stage IIIA melanoma, which could potentially have significant clinical impact by identifying those Stage IIIA patients who would benefit from adjuvant therapies,” commented lead study investigator Martin D. Fleming, M.D., FACS, Chief of Surgical Oncology and Associate Professor of Surgery at University of Tennessee Health Science Center. “Additionally, the performance of the GEP test in the group of patients who underwent completion lymph node dissection, suggests that the test may be valuable in guiding use of the CLND procedure.”

Multicenter Validation Study of Head and Neck Melanoma
In the abstract, “Performance of a 31-gene expression profile (GEP) test for metastatic risk prediction in cutaneous melanomas (CM) of the head & neck” (Abstract #9576), results from 157 patients with cutaneous melanoma of the head and neck region were reported.

Primary endpoints of the study were RFS, DMFS, and MSS. Survival rates by SLN status include clinically node-negative patients.

Highlights of Study Results:

In a cohort of head and neck melanoma patients, the DecisionDx-Melanoma test identified 88% (22 of 25) of patients who died from their disease as Class 2. Results for MSS according to DecisionDx-Melanoma subclass are shown in the table below:

Patients with a low-risk Class 1A result showed lower RFS, DMFS, and MSS event rates than those with node-negative status.

Patients with a high-risk Class 2B result had similar RFS, DMFS and MSS rates as those with node-positive status.

DecisionDx-Melanoma testing could be a clinically useful tool for patients with melanoma of the head and neck following a node-negative result to identify those patients who may still be at high risk for metastasis.

“The results of these three studies presented at the ASCO meeting provide new, confirmatory data that our DecisionDx-Melanoma test demonstrates consistent accuracy across different patient cohorts, providing reliable prognostic information,” added Federico A. Monzon, M.D., FCAP, Chief Medical Officer of Castle Biosciences of Castle Biosciences. “Clinicians across the U.S. are now relying on the DecisionDx-Melanoma test to provide individualized and accurate prognostic information to assess risk of recurrence and plan follow-up care.”

About DecisionDx-Melanoma
The DecisionDx-Melanoma test uses tumor biology to provide a prediction of individual risk of melanoma recurrence beyond traditional factors. Using tissue from the primary melanoma, the test measures the expression of 31 genes. The test has been validated in three multicenter studies that have included 690 patients and have demonstrated consistent results. Performance has also been confirmed in three independent, prospective studies including 510 patients. The consistent high performance and accuracy demonstrated in these studies, which combined have included 1200 patients, provides confidence in disease management plans that incorporate DecisionDx-Melanoma test results. Clinical impact has been demonstrated in a multicenter and single-center study showing that test results add additional patient-specific prognostic information to complement traditional staging tools. More information about the test and disease can be found at www.SkinMelanoma.com.

About Castle Biosciences
Castle Biosciences is a molecular diagnostics company dedicated to helping patients and their physicians make the best possible treatment and follow-up care decisions based on the individual molecular signature of their tumor. The Company currently offers tests for patients with cutaneous melanoma (DecisionDx®-Melanoma; www.SkinMelanoma.com) and uveal melanoma (DecisionDx®-UM and DecisionDx®-PRAME; www.MyUvealMelanoma.com), with development programs in other underserved cancers. Castle Biosciences is based in Friendswood, TX (Houston), and has laboratory operations in Phoenix, AZ. More information can be found at www.CastleBiosciences.com.

DecisionDx-UM, DecisionDx-Melanoma and DecisionDx-PRAME are the trademarks of Castle Biosciences, Inc. Any other trademarks are the property of their respective owners.